The violence that forced the cancellation of a controversial Sikh play was caused by militant extremists who aligned themselves to the protest, organisers claimed yesterday.

The Sikh community fears that its reputation has been tarnished by the trouble at the Birmingham Repertory Theatre, which led to the play Behzti (Dishonour) being abandoned.

The Times has learnt that members of the Sikh Federation were among the demonstrators on Saturday night. The group was formed in the aftermath of the banning of the International Sikh Youth Federation under the Terrorism Act 2000. The I.S.Y.F. is committed to the creation of an independent Sikh state in India and, according to the Foreign Office, has been involved in assassinations, bombings and kidnappings, mainly directed against Indian officials and interests.

The Sikh Federation maintains that it is separate from the I.S.Y.F., with a new constitution and an agenda of promoting Sikh interests in Britain. It said that strict disciplinary arrangements would apply to the members who brought the organisation into disrepute 'by working outside the legitimate activities of the organisation.' It added: 'The ultimate sanction against a member will be expulsion.'

Kulwinder Singh Johal, from Leicester, a member of the federation, said he was pleased that Behzti had been withdrawn and confirmed that members of the federation had been involved in the campaign against the play.

'There was no violence, it has been exaggerated,' he said. 'A window was smashed, but we don't know if that was done from the outside or the inside.'

Amrik Singh Gill, chairman of the federation, said his members were involved in the campaign from the beginning and denied they played any part in violence. 'They were all peaceful people and were there to protest peacefully,' he said. 'I condemn the violence.'

West Midlands Police, who arrested three demonstrators and are trying to identify others, are investigating whether the violence was pre-planned.

Sewa Singh Mandla, the chairman of the Council of Sikh Gurdwaras in Birmingham who organised the campaign against the play, said he was dismayed that it had been dropped in the face of the weekend violence. He said that, as the play received more media attention, a host of organisations were jostling to become involved. 'The Sikh Federation is just jumping on the bandwagon,' Mr. Mandla said.

'They are a group of militant people who just want to stir up problems around us.'

Mr. Mandla had hoped that the play might have been altered to change the setting of controversial scenes involving rape and murder from a Sikh temple to a community centre.

He added: 'I knew what the feeling would be if it got into the public domain - anything could happen. There would be demonstrations and every community has hotheads and, once they turn up, I would find it very hard to control them.

'I was at pains to tell people that the protest had to be peaceful. When it became national news, people came from Leicester, Leeds, London and Manchester. When it became violent, I was pushed and jostled by people. They called me a sissy and told me to resign.

'There was a peaceful group of people reciting prayers in the corner. Others who were chanting were the ones who burst into the theatre. Some of them did not seem to be Sikhs.

'The play has been taken off but the reasons why sadden me. It's not conducive to good community relations.

'I would like to apologise on behalf of the Sikh community to all the people who had to be evacuated from the theatre on Saturday. It was just a small faction which got out of hand.'

Sukhjinder Singh, from the Sikh Secretariat, an advisory body, said the different community groups needed to examine how they could have better organised their protest. 'Nobody is saying this is a fantastic victory for the Sikh community,' he said. 'A legitimate protest was marred by violence.'